Study on Damage and Repair Mechanical Characteristics of Rock Salt Under Uniaxial Compression

Abstract

Damage and self-healing characteristics of rock salt are key factors for the evaluation of underground salt cavern safety. During the construction of a salt cavern, characteristics of the surrounding rock (formation temperature, pressure and brine saturation) can affect the self-healing of rock salt. To study the recovery effect, we carried out a study through uniaxial compression tests. The rock salt samples were divided into group S and group X: samples in group X were annealed after initial damage (damage point: 15 Mpa, 20 Mpa, 25 Mpa and peak stress) while the samples in group S were not. For group S, a peak damage was applied immediately after the initial damage. Group X samples, after initial damage, were placed in the repair environment for 7 days. The repair environment mentioned above is set as saturated brine with a temperature of 50 °C and pressure of 12 MPa. It turned out that (1) the rock salt has almost no compaction phase during uniaxial compression. Damaged rock salt experienced an apparent compaction stage after being repaired; (2) for all the samples in the two groups, the yield stress and elastic modulus increase after the initial damage, which is regarded as the hardening of rock salt; (3) the plasticity of damaged rock salt can significantly recover after having been repaired. Thus, the environment during the construction of a salt cavern has a good effect on the self-healing of rock salt, and this characteristic of rock salt is beneficial to the safe operation of a cavern for storage purposes.